The present invention relates to a catalyst used in hydrorefining of hydrocarbons, such as petroleum fractions, and a method of producing the same, and particularly relates to a catalyst used in hydrodemetallization of heavy fractions and residue of various types that are obtained by normal-pressure distillation or reduced-pressure distillation of heavy oils, such as crude oil, tar sand, shale oil, coal liquefaction oil.
Heavy oil, such as residue from normal-pressure distillation or reduced-pressure distillation residue, comprises a high metal content of nickel, vanadium, etc. This metal content poisons hydrorefining catalysts for desulfurization, denitrification, cracking, etc., and reduces their catalytic activity and, therefore, is pre-treated with hydrorefining catalysts for the purpose of demetallization (also referred to hereafter as demetallizing catalysts).
It is known that although these demetallizing catalysts have the same median pore diameter and support the same active metal species, there are considerable differences in their demetallizing activity and metal deposition capacity (amount of metal that can deposit inside the pores until the catalyst loses activity). This appears to be due to the fact that there are differences in pore diameter distribution and catalyst structure in other ways. For example, when a catalyst having a pore volume almost all of which is pores with a pore diameter of 60 nm or smaller is used as a demetallizing catalyst, demetallizing activity is high, but large amounts of metal deposit around the pore inlets and metal deposition capacity is reduced because the pore inlets are clogged. In contrast to this, when a catalyst (bimodal catalyst) having a pore group with a pore diameter of 60 nm or smaller (mesopores) and a pore group whose pore diameter exceeds 60 nm (macropores) is used, metal deposition capacity can be increased, but there is a relative drop in demetallizing activity.
Japanese Patent Publication No. 60-49135 (Rhxc3x4ne-Poulenc Industries) and Japanese Patent Application Laid-Open No. 6-88081 (Texaco Development Corporation) are known as conventional bimodal catalysts of this type. Nevertheless, in reference to the present invention, although the former discloses a spherical carrier, there is no mention whatsoever of the catalyst being used for a demetallization reaction. The latter reference tells of a carrier with a total pore volume of 0.5 to 0.8 cm3/g, but metal deposition capacity of this catalyst is not high.
That is, a hydrorefining catalyst with both a high demetallizing activity and a high metal deposition capacity has not existed in the past.
An object of the present invention is to present a hydrorefining catalyst with both high demetallizing activity and high metal deposition capacity, and a method of producing the same.
In accordance with the first aspect of the present invention, a hydrorefining catalyst is provided comprising a hydrogenation active metal component supported on a refractory porous carrier, wherein median pore diameter determined by the nitrogen adsorption method is 8 to 20 nm, pore volume determined by a nitrogen adsorption method is 0.56 cm3/g or greater, and pore volume of pores with a pore diameter of 50 nm or larger determined by a mercury intrusion porosimetry method is 0.32 cm3/g or greater.
Both the demetallizing activity and metal deposition capacity of the hydrorefining catalyst of the present invention for hydrorefining, particularly hydrodemetallization, can be increased by bringing the median pore diameter, pore volume of pores (pores having a pore diameter of approximately 60 nm or smaller) determined by the nitrogen adsorption method, and pore volume of pores that were determined by the mercury intrusion porosimetry method and that have a pore diameter exceeding 50 nm to values within the above-mentioned prescribed ranges. As a result, long-term retention of a high metal content removal percentage is possible. For instance, it was clarified that the hydrorefining catalyst of the present invention has a high effective amount of metal deposition of 70 g or more per 100 g fresh catalyst under conditions defined later. The catalyst of the present invention is particularly suitable for demetallizing or deasphaltening of heavy oil.
It is preferred that the hydrorefining catalyst of the present invention have a pore volume determined by the mercury intrusion porosimetry method of 0.87 cm3/g or greater so that it will have even better demetallizing activity. Moreover, in order to obtain sufficient mechanical strength, the hydrorefining catalyst should have a pore volume of pores of 0.2 cm3/g or greater which is determined by the mercury intrusion porosimetry method and having a pore diameter of 1,000 nm or larger. In addition, bulk density can be brought to 0.52 cm3/g or less because the catalyst of the present invention has high demetallizing activity. As a result, it is possible to reduce the load on the reaction vessel in which the catalyst has been packed and the durability of the reaction vessel can therefore be improved, even if differential pressure is somewhat high.
The hydrorefining catalyst of the present invention may comprise 2 to 6 wt % molybdenum and 0.5 to 2 wt % nickel or cobalt, as hydrogenation active metal components. The hydrorefining catalyst of the present invention may further comprise 0.5 to 1.5 wt % phosphorus or boron.
In accordance with a second aspect of the present invention, a method of producing a hydrorefining catalyst is provided comprising the steps of kneading a porous starting powder whose main component is xcex3-alumina and which has a pore volume of 0.75 cm3 g/or greater and an mean particle diameter of 10 to 200 xcexcm to prepare a kneaded product; molding and calcining said kneaded product; and supporting active metal component on the kneaded product or on the kneaded product after calcining. With the method of the present invention, since a porous powder that comprises xcex3-alumina powder as its main component and has the above-mentioned prescribed pore volume and mean particle diameter is used as the starting material, it is possible to easily produce at a low cost a hydrorefining catalyst with both a high demetallizing activity and a high metal deposition capacity and a catalyst carrier used by the same.
In this text, the term xe2x80x9cxcex3-alumina as the main componentxe2x80x9d means that 70 wt % or more of the starting powder is xcex3-alumina. The remainder may be, for instance, boehmite, such as pseudoboehmite, etc. In order to improve the demetallizing activity and metal deposition capacity of the catalyst even further, it is preferred that 90 wt % or more, particularly 95 wt % or more, of the starting powder be xcex3-alumina. It is further preferred that approximately 100% of the starting powder be xcex3-alumina powder. The term xe2x80x9cxcex3-aluminaxe2x80x9d in the present text means transition alumina with peaks at 2xcex8=46xc2x0 and 67xc2x0 in X-ray diffraction at a wavelength of 0.154 nm. Preferably, xcex3-alumina is prepared by calcining boehmite powder. The boehmite powder in the present specification means a boehmite or pseudoboehmite powder. Furthermore, pseudoboehmite is an xcex1-alumina hydrate with excess water molecules in the crystals and is represented by Al2O3.XH2O, with X being 1 or more and less than 2.
In terms of molding cost and the high percentage of void of the catalyst carrier, it is preferred that molding be performed by, for instance, extrusion molding using a molding device in the method of producing a hydrorefining catalyst of the present invention.